If the stock bores were that bad then the stock OEM motors would never pass an emissions test. (blowby and oil contamination would give huge unburned hydrocarbons) They tend to pass strict emissions tests so the ring seal quality must be pretty good.
Check/measure the dish volume of your pistons. (its not that hard to do) If they are -12 to -15cc mill your vortec heads .040" and install with with the .015" shim gasket. the stock 350 pistons should be .025" below deck @ TDC or close to it.
Your cr will be between 9.6 and 9.8:1 finished with a 58-60cc head volume.
Thats plenty enough compression for a street motor.

GM doesn't recomend flat milling more than .040" off the deck of these heads.
The physical flat mill limit is the stock intake valve seat edge.
You'll be fine at .040".

About the only way to keep it low buck.

Have you ever measured a block with a torque pate installed??? As I posted stock engines don't build alot of cylinder pressure compared to a performance engine.

Look at a set of stock pistons they blowby all the way to the oil rings.

CNC: I don't doubt or question you skills and knowledge on proper race engine block preparation or the value of using a torque plate when honing,

I don't even know if GM hones the blocks with a torque plate attached or not, I'd bet they do. I'll ask some one that works on the line at GM St. Catharines ( Engine Plant) next time, if they do or.....

F-BIRD

We buy alot of new blocks form GM and NO they do not plate hone their blocks and we have seen quite a few of the crate engines out of cicle track cars and have gone though them and those are not plate honed either.

Stock engines run very lean compared to a performance engine and there is very little byproduct from the combustion proccess.

Over the years we have done a few rebuilds for friends and have gone through the blocks the right way line hone, deck, bore and plate hone and the engines have run better then they did when they were new and the fuel milage improved alot as well..

On other thing to remember that GM bores the cylinders off the pan rails Which is not very accurate, Some time take a depth mike and measure the depth of the main housing bores from the pan, We have found that the pan rail and the crank center lines are off a lot. Would a guy ever deck of the pan rail ?? GM blocks are machined very crude compared the Bowtie blocks.

Regardless of how GM does it, you won't be able to rehone your block without going oversize in some way. The block was honed to fit your pistons, then the rings wore it larger, then honing it again will make it bigger yet.

The deck should be checked for flatness, but if you don't need to shave it, don't. No need to make the decks thinner if they don't need to be... just like you're not anxious to overbore unless you need to. With flat tops .020 in the hole plus your .015 gasket will make a nice tight quench.

Most good shops wait for the pistons to come in so they can measure that specific set and do final honing for your pistons.

One day I'm going to do the plant tour there and see just what they do.
They build the LS V8 motors and the V6's there. Used to do the Gen 1 vortec V8 motors before. My friends dad was a lead hand there years ago and would know exactly what they do/did...don't. Used to get us lots of cool SBC engine parts for building our hot rods, way back.

I don't doubt for a minute that you can and do improve on GM's crate motors but I'm assuming this posters motor is low mileage and in good overall condition and should be fine for a low buck budget build up. Got to keep the costs in check or its no longer a "budget build."

I didn't see any where that this was a budget build!!!!

In most cases budget builds don't come out as good as non budget engines as have seen quite a few budget engines over the years that other shops have built on a budget and the customers are not happy with the results and in most cases they were promised they would be happy with the power. So we have seen more then one guy rebuild there engine the right way.

Regardless of how GM does it, you won't be able to rehone your block without going oversize in some way. The block was honed to fit your pistons, then the rings wore it larger, then honing it again will make it bigger yet.

The deck should be checked for flatness, but if you don't need to shave it, don't. No need to make the decks thinner if they don't need to be... just like you're not anxious to overbore unless you need to. With flat tops .020 in the hole plus your .015 gasket will make a nice tight quench.

Most good shops wait for the pistons to come in so they can measure that specific set and do final honing for your pistons.

It's important to have the decks square to the main line and a true 45 degrees from the cam and crank center lines.

We have seen blocks that shops bore off an unsquared decks and in most cases if the block won't go .060 because it didn't pass a sonic test its know junk.

If your going to have a block machined for performance use do it once right as it makes for a much better running engine in the end.

Ther are a lot of shops out there doing shorty work because thay don't have the proper equipment to do it right, Don't get me wrong building a bone stock engine you can get away with a lot but building performance engines the substandard machine work will show up after a while.

There is a right way to do things and I guess there is a semi right way LOL.

1. have the block decked JUST enough to make sure Ihave it indexed 90 degrees to the crank.

2. have a flat surface for optimum sealing for the .015 steel shim head gasket.

3. have the heads checked for flatness and milled if needed. Perhaps .020.

4. I am considering an .30 overbore to fit a set of pistons. I have seen these and am wondering if they are ok or not. I was looking for something with less than +7.00 cc. +5 cc sounds good if I want to keep the compression up.These Pistons from Summit.

It seems silly to me to get a .015 head gasket, mill everything & then go to a +7 cc flat top piston.

You need to set a goal, a realistic goal. Then, no matter what you use, or how you go about getting there, make your goal. IMO those are el cheapo cast pistons, and sure they'd work, but what is it you are going to do with this engine? You could throw them in and add some cam along with some budget priced stuff and get what you want, or, go whole hog and make it exactly what you want without worry. First thing though, you need a specific goal for this engine and need to know where it is going to spend it's life, happily.

You need to set a goal, a realistic goal. Then, no matter what you use, or how you go about getting there, make your goal. IMO those are el cheapo cast pistons, and sure they'd work, but what is it you are going to do with this engine? You could throw them in and add some cam along with some budget priced stuff and get what you want, or, go whole hog and make it exactly what you want without worry. First thing though, you need a specific goal for this engine and need to know where it is going to spend it's life, happily.

Exactly what you wrote. Firstly, I am a technical guy by trade, Industrial Electrican and HVAC. I am no stranger to wrenching on machinery like motorcycles 2 & 4 stroke. I have experience in setting up Harley motors & transmissions. I like to wrench stuff. My father owned a VW motor rebuilding shop that built motors both for sale to the public & for machine shops. I worked there at times for extra money. I am within spitting distance of retirement, so money is of concern.

I have modified 2 auto engines, and been disappointed in both.

I would like a truck built around a 350 sbc. When I step on the gas, I would like it to go as fast or faster than traffic. mileage is not an issue with me. I am willing to give up some bottom end torque for some scoot. My plans are to address the rear end with 3.73 or 4.11 gears, coupled to a stall converter with around a 2600-3000 stall to work with the cam that was recommended.

All of my motors in the past have been built around 79cc heads, and I have learned the low compression is one heck of a hurdle in the pursuit of decent HP.

What I am learning now is the importance of proper quench and thee role it plays in compression, detonation and proper spark curve. I am learning this stuff and some here are helping me a great deal.

Some are forthcoming with the help, and others have to have the information dragged out of them with an engine hoist. I like the attitude of F-bird'88. Tech-inspector is another wise one, but sometimes he comes across as a bit condescending.

If indexing the block and heads is a requirement (born of experience and knowledge of others) for a proper motor set up, then this I will have to do. I have in the past always asked for a rebore when fitting new pistons. From what I know, pistons were always bored undersized then honed for each piston clearance. Maybe things are different now.

I need to be able to call on others to tell me if I am going cheap (bad!) or bargain with my parts selection. Some stuff is a bargain because it has been out there for a zillion years. That does not make it a cheap part.

This is my F-bird'88 suggested build:

a basic 350ci SBC short block with flat top pistons
+ 062 or 906 GM vortec heads
Isky #205D valves springs minus the inner damper
Stock OEM vortec retainers, seals locks and rocker arms
Isky #201278 camshaft 278-278 .450" .450" lift 234-234@.050" 106° LSA
Edelbrock Performer RPM Manifold and 750cfm 4bbl carb
1-5/8" headers 2.5" dual exhaust.
This combo makes more power and torque than the Edelbrock RPM cam will make without needing vortec cylinder head machining modifications to accomodate the .488"-.510" valve lift of the Edelbrock RPM camshaft.
Should use a 10" high stall torque converter and 3.73 to 4.10 rear gearing for best results. (same as the rpm cam needs)
Isky #201288 will make even more top end power all with just .450" valve lift.
Degree the cam in on a 102°-103° intake C/L for best results.

All help is appreciated always.
I am not so smart as to know everything there is about this subject, and I am smart enough to know that. This is where you guys come in.

Your success is going to be shared, and I thank you for that. I really do.

You don't need to machine for the performer rpm can, just use the old style o-ring type valve seals (don't use the umbrella seals!). That will get you around 525" lift with the vortec heads.
I've ran 510" roller cams on them with no machine work whatsoever spinning 6200 rpm. basically the exact same setup fbirds saying..intake and all.

You don't need to machine for the performer rpm can, just use the old style o-ring type valve seals (don't use the umbrella seals!). That will get you around 525" lift with the vortec heads.
I've ran 510" roller cams on them with no machine work whatsoever spinning 6200 rpm. basically the exact same setup fbirds saying..intake and all.

If you don't use the oil shields with the o-ring seals you will have an oil burner. Using the oil shield will set the springs up .030" tighter. You'll probably need to cut the spring pocket deeper or use a +.050" keeper. Kinda negates the easy fix of using the o-ring seal.

1. have the block decked JUST enough to make sure Ihave it indexed 90 degrees to the crank.

2. have a flat surface for optimum sealing for the .015 steel shim head gasket.

3. have the heads checked for flatness and milled if needed. Perhaps .020.

4. I am considering an .30 overbore to fit a set of pistons. I have seen these and am wondering if they are ok or not. I was looking for something with less than +7.00 cc. +5 cc sounds good if I want to keep the compression up.These Pistons from Summit.

It seems silly to me to get a .015 head gasket, mill everything & then go to a +7 cc flat top piston.

I need help with this guys, there is so much stuff to keep track of.

Those pistons are bottom of the barrel, stock, rebuilder pistons. They are heavy and are decked .020". Look for something that is hypereutectic and a little lighter that isn't decked. The H345NCP by Sealed Power (Speed-Pro) would be a better choice. Plus, you don't have to run a bigger top ring gap, which you would have to do with a Keith Black hypereutectic.

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